ATP series firmware: Improper Neutralization of Special Elements used in an OS Command
CVE-2023-6398 is a high-severity improper neutralization of special elements used in an OS command vulnerability in ATP series firmware from Zyxel, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected ATP series firmware versions: version 4.32 through 5.37 Patch 1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.33% chance of exploitation within 30 days, higher than 72% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update NWA50AX firmware to 6.29\(abyw.4\) or a later version.
- Update WAC500 firmware to 6.70\(abvs.1\) or a later version.
- Update WAX300H firmware to 6.70\(achf.1\) or a later version.
- Read the advisory on zyxel.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Zyxel | ATP series firmware | version 4.32 through 5.37 Patch 1 | Not stated |
| Zyxel | USG FLEX series firmware | version 4.50 through 5.37 Patch 1 | Not stated |
| Zyxel | USG FLEX 50(W) series firmware | version 4.16 through 5.37 Patch 1 | Not stated |
| Zyxel | USG20(W)-VPN series firmware | version 4.16 through 5.37 Patch 1 | Not stated |
| Zyxel | NWA50AX firmware | < 6.29(ABYW.4); before 6.29\(abyw.4\) | 6.29\(abyw.4\) |
| Zyxel | WAC500 firmware | < 6.70(ABVS.1); before 6.70\(abvs.1\) | 6.70\(abvs.1\) |
| Zyxel | WAX300H firmware | < 6.70(ACHF.1); before 6.70\(achf.1\) | 6.70\(achf.1\) |
| Zyxel | WBE660S firmware | < 6.70(ACGG.1); before 6.70\(acgg.1\) | 6.70\(acgg.1\) |
| Zyxel | USG FLEX H series firmware | version 1.10 through 1.10 Patch 1 | Not stated |
| Zyxel | atp800_firmware | 4.32 through 5.37_patch1 | Not stated |
| Zyxel | usg_flex_700_firmware | 4.50 up to, but not including, 5.37_patch1 | 5.37_patch1 |
| Zyxel | usg_20w-vpn_firmware | 4.16 through 5.37_patch1 | Not stated |
| Zyxel | Atp100 Firmware | 4.32 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Atp100w Firmware | 4.32 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Atp200 Firmware | 4.32 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Atp500 Firmware | 4.32 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Atp700 Firmware | 4.32 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 100 Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 100ax Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 100h Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 100w Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 200 Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 200h Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 200hp Firmware | 4.50 up to, but not including, 5.37; 5.37 | 5.37 |
| Zyxel | Usg Flex 50 Firmware | 4.16 up to, but not including, 5.37; 5.37 | 5.37 |
Version data comes from the organisation that assigned the CVE; 23 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (zyxel.com.tw).
Official description
A post-authentication command injection vulnerability in the file upload binary in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1, USG FLEX series firmware versions from 4.50 through 5.37 Patch 1, USG FLEX 50(W) series firmware versions from 4.16 through 5.37 Patch 1, USG20(W)-VPN series firmware versions from 4.16 through 5.37 Patch 1, USG FLEX H series firmware versions from 1.10 through 1.10 Patch 1, NWA50AX firmware versions through 6.29(ABYW.3), WAC500 firmware versions through 6.65(ABVS.1), WAX300H firmware versions through 6.60(ACHF.1), and WBE660S firmware versions through 6.65(ACGG.1) could allow an authenticated attacker with administrator privileges to execute some operating system (OS) commands on an affected device via FTP.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in an OS Command
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in ATP series firmware
- 7.2 High severity
- 7.2 High severity
- 8.1 High severity
- 7.2 High severity
- 9.8 Critical severity
Zyxel Multiple Firewalls Path Traversal Exploited
- 7.2 High severity
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 9.8 Critical severity
- 8.8 High severity
- 9.8 Critical severity
- 7.5 High severity
- 9.8 Critical severity
- 9.1 Critical severity
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